Solid-state polymeric materials based on oxygen-sensitive photoluminescent dyes are widely used as optical oxygen sensors and probes. See, for example United States Published Patent Applications 2009/0029402, 2008/8242870, 2008/215254, 2008/199360, 2008/190172, 2008/148817, 2008/146460, 2008/117418, 2008/0051646, and 2006/0002822, and U.S. Pat. Nos. 7,569,395, 7,534,615, 7,368,153, 7,138,270, 6,689,438, 5,718,842, 4,810,655, and 4,476,870. Such optical sensors are available from a number of suppliers, including Presens Precision Sensing, GmbH of Regensburg, Germany, Oxysense of Dallas, Tex., United States, and Luxcel Biosciences, Ltd of Cork, Ireland.
Such oxygen-sensitive photoluminescent dyes respond to the partial pressure of oxygen (PO2), and are widely used in pressure-sensitive paints that can be applied to the surface of an object and interrogated to determine pressure distribution on the surface of the object. See, for example United States Published Patent Applications 2007/112166, 2007/105235, 2006/101906, 2005/288475, 2004/0249593, 2004/091695, and 2003/175511, and U.S. Pat. Nos. 7,290,444, 7,176,272, 7,127,950, 5,965,642, 5,854,682, 5,818,057, 5,612,492, 5,359,887, 5,341,676, 5,307,675, and 5,186,046.
Manufacturers and suppliers of labile products, such as medical and biological products, pharmaceuticals and foodstuffs, typically package such products in a hermetically sealed package that has been flushed with an inert gas, such as nitrogen, for purposes of reducing the concentration of oxygen within the package and thereby increasing the shelf-life of the product. It is known to employ oxygen sensitive optical probes within such packaging for providing a quick, easy, reliable and non-destructive means for measuring the concentration of oxygen within the packaging, from which the manufacturer can evaluate the integrity of the packaging process and/or the shelf-life status of packaged product in inventory. See, for example United States Published Patent Application 2009/0028756.
Manufacturers and suppliers of such labile products also often desire to measure the pressure within the package instead of or in addition to measuring the concentration of oxygen, again for purposes of evaluating the integrity of the packaging process and/or evaluating the remaining shelf-life of packaged product in inventory (e.g., an increase in pressure within a bag of potato chips is indicative of deterioration of the chips and resultant loss of taste and shelf-life while a decrease in pressure within a bottle of a carbonated beverage is indicative of a loss of carbonation and resultant loss of taste and shelf-life). Unfortunately, the current methods available to manufacturers and suppliers for measuring pressure within a hermetically sealed package are prohibitively slow and cumbersome or destructive of the package being tested.
Hence, a substantial need exists for a quick, easy, reliable and non-destructive means for measuring the pressure within hermetically sealed packaging.